Projector array for multiple images

ABSTRACT

A centralization point in a projection area is designated. The projection area is on a projection surface onto which images are projected by a projector array, which includes a plurality of projectors. A first image is projected in a first maximum area rectangle at a first aspect ratio of the first image, and the first image is projected into the projection area centered at the centralization point. A second image is projected in a second maximum area rectangle at a second aspect ratio of the second image, and the second image is projected into the projection area centered at the centralization point.

BACKGROUND

1. Field

The present disclosure relates to image projection and, morespecifically, to display of multiple images by a projector array into aprojection area on a projection surface.

2. Background

Keystone correction is typically used to correct an image beingprojected by a projection system, in which the image would otherwise bedistorted principally due to an angle of projection from the projectionsystem to the projection surface (e.g., projection screen). Typically,keystone correction is applied to a projection system so as to obtain ahomography transformation that results in good image fidelity between asource image and a projected image. When the projection system includesmultiple projectors in a projector array, the homography transformationis ordinarily derived for a single object, regardless of the number ofobjects actually formed by the projection system.

As such, using keystone correction in a projection system with multipleprojectors in a projector array may cause image distortion anddistraction for viewers. Accordingly, there is a desire to improve imagequality when performing such keystone correction.

SUMMARY

Disclosed embodiments describe the display of images with a projectorarray comprising a plurality of projectors. Images are projected into aprojection area so as to maintain the center of the projected images ata fixed centralized point, which is used for all of the multiple images,while also projecting the images at the aspect ratio of each image andat their largest size within the projection area.

Thus, in an example embodiment described herein, a projector arrayincludes a plurality of projectors, which together, project images intoa projection area on a projection surface. A centralization point in theprojection area is designated. A first image is projected in a firstmaximum area rectangle at a first aspect ratio of the first image, andthe first image is projected into the projection area centered at thecentralization point. A second image is projected in a second maximumarea rectangle at a second aspect ratio of the second image, and thesecond image is projected into the projection area centered at thecentralization point.

By virtue of this arrangement, it is ordinarily possible to project oneor more images with reduced keystone distortions while automaticallycentering the projected images at an identified centralized point, whilealso providing dynamic aspect ratio adjustment such that the images areat their maximum size, scaled at their respective aspect ratio, andprojected within the projection area.

In example embodiments, the projection area is detected by cornerdetection using an image capture device which captures an image of theprojection surface. The image capture device can include a camera, suchas a digital camera.

In other example embodiments, the first maximum area rectangle isdetermined at the first aspect ratio within the projection area. Thecenter of the first maximum area rectangle is identified as thecentralization point. The second maximum area rectangle is determined atthe second aspect ratio within the projection area. The second maximumarea rectangle is determined by calculations using the second aspectratio and the centralization point, so as to result in a substantiallymaximum area within the projection area centered at the centralizationpoint.

In yet other example embodiments, a first homography matrix isdetermined based on the determination of the first maximum arearectangle. A first inverse homography matrix transform is applied to thefirst homography matrix, and a first homography-transformed image of thefirst image is obtained based on the first inverse homography matrix andthe first aspect ratio. a second homography matrix is determined basedon the determination of the second maximum area rectangle. A secondinverse homography matrix transform is applied to the second homographymatrix, and a second homography-transformed image of the second image isobtained based on the second inverse homography matrix and the secondaspect ratio.

This brief summary has been provided so that the nature of thisdisclosure may be understood quickly. A more complete understanding canbe obtained by reference to the following detailed description and tothe attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a representative view of a multiprojector system relevant toone example embodiment.

FIG. 2 is a detailed block diagram depicting the internal architectureof the host computer shown in FIG. 1.

FIG. 3 is a view for explaining software architecture of a controlmodule for a multiprojector system according to an example embodiment.

FIG. 4 is a flow diagram for explaining control of a multiprojectorsystem according to an example embodiment.

FIGS. 5A and 5B show, schematically, an example of a series of projectedimages according to the flow diagram shown in FIG. 4.

FIG. 5C shows, schematically, an example showing the determination of asecond or a subsequent maximum area rectangle not in accordance with theflow diagram of FIG. 4.

DETAILED DESCRIPTION

FIG. 1 is a representative view of a multiprojector system 100 includinga projector array comprised of projectors 50 to 52, a host computer 40and camera 55, relevant to one example embodiment. Host computer 40generally comprises a programmable general purpose personal computer(hereinafter “PC”) having an operating system such as Microsoft®Windows® or Apple® Mac OS® or LINUX, and which is programmed asdescribed below so as to perform particular functions and in effect tobecome a special purpose computer when performing these functions. Hostcomputer 40 includes a color monitor including a display screen, akeyboard for entering text data and user commands, and a pointingdevice. Pointing device preferably comprises a mouse for pointing andfor manipulating objects displayed on the display screen.

Host computer 40 also includes computer-readable memory media such as acomputer hard disk and a DVD disk drive, which are constructed to storecomputer-readable information such as computer-executable process steps.The DVD disk drive provides a means whereby the host computer can accessinformation, such as image data, computer-executable process steps,application programs, etc. stored on removable memory media. In analternative, information can also be retrieved through othercomputer-readable media such as a USB storage device connected to a USBport, or through a network interface. Other devices for accessinginformation stored on removable or remote media may also be provided.

Host computer 40 may acquire image data from other sources such as adigital camera, a local area network or the Internet via a networkinterface. Likewise, host computer 40 may interface with color outputdevices other than projectors 50 to 52, such as color output devicesaccessible over the network interface.

Host computer 40 acquires image data for an input image, and providespre-distorted image data to each of projectors 50 to 52 such thatcorresponding image 60 is displayed on a projection surface with reducedkeystone distortion. In addition, the image data is provided for displayby projectors 50 to 52 such that the image 60 is displayed at itslargest size while maintaining the aspect ratio of the image anddisplaying the images at a single centralization point based on a firstdisplayed image in a sequence of images.

In this example, projectors 50 to 52 are RGB or RGBW projectors, such asDLP™ digital projectors or other display devices that project images inaccordance with image data from the host computer 40 onto a projectionsurface. Projectors 50 to 52 may be HDR devices capable of projectingHDR images, and may further include, for example, LCD projectors, LCOSprojectors, LED projectors.

Together, projectors 50 to 52 make up a projector array, and inaccordance with image data received from host computer 40, projectors 50to 52 project image 60 onto a projection screen by using additive lightcombinations of red (R), green (G) and blue (B) colorant lights. Inaddition, and particularly in a case of an HDR device, projectors 50 to52 also use a white (W) light so as to increase the brightness/luminanceof projected images and thereby project HDR images with good fidelityover a large dynamic range.

Digital color camera 55 is an example of a color input device, and isprovided for sending digital image data to host computer 40. Inparticular, digital color camera 55 captures images of the projectionsurface of the projector array in order to facilitate control of themultiprojector system.

FIG. 1 shows an example of a projector array where projectors 50 to 52are positioned to form one single image 60. As shown in FIG. 1,projector 50 displays individual projection area A, projector 51displays individual projection area B and projector 52 displaysindividual projection area C. In other words, individual projectionareas A, B and C are respectively displayed by projectors 50, 51 and 52.In this example, image data is provided by host computer 40 such thateach of projectors 50 to 52 displays the appropriate portion of image 60on the single object on the projection surface.

FIG. 2 is a detailed block diagram showing the internal architecture ofhost computer 40. As shown in FIG. 2, host computer 40 includes centralprocessing unit (CPU) 113 which may be a multi-core CPU and whichinterfaces with computer bus 114. Also interfacing with computer bus 114are fixed disk 45, network interface 109, random access memory (RAM) 116for use as a main run-time transient memory, read only memory (ROM) 117,DVD disk interface 119, display interface 120 for a monitor, keyboardinterface 122 for a keyboard, mouse interface 123 for a pointing device,digital projector interface 124 for projector 50, digital projectorinterface 125 for projector 51, digital projector interface 126 forprojector 52, and digital camera interface 127 for digital camera 55.

RAM 116 interfaces with computer bus 114 so as to provide informationstored in RAM 116 to CPU 113 during execution of the instructions insoftware programs such as an operating system, application programs,control modules, and device drivers. More specifically, CPU 113 firstloads computer-executable process steps from fixed disk 45, or anotherstorage device into a region of RAM 116. CPU 113 can then execute thestored process steps from RAM 116 in order to execute the loadedcomputer-executable process steps. Data such as color images or otherinformation can be stored in RAM 116, so that the data can be accessedby CPU 113 during the execution of computer-executable softwareprograms, to the extent that such software programs have a need toaccess and/or modify the data.

As also shown in FIG. 2, fixed disk 45 stores computer-executableprocess steps for operating system 130, and application programs 131,such as graphic image management programs. Fixed disk 45 also storescomputer-executable process steps for device drivers for softwareinterface to devices, such as input device drivers 132, output devicedrivers 133, and other device drivers 134, such as drivers forprojectors 50, 51 and 52. Image files 141, including color image files,and other files 142 are available for output to color output devices andfor manipulation by application programs.

Control module 145 comprises computer-executable process steps executedby a computer for control of a multiprojector system, where themultiprojector system includes multiple projectors arranged in aprojector array. Control module 145 controls the multiprojector systemsuch that an image is projected into a projection area on a projectionsurface. Briefly, control module 145 controls the projector array sothat a first image is projected in a first maximum area rectangle at afirst aspect ratio of the first image. A centralization point of thefirst maximum area is determined. The first image is projected into theprojection area centered at the centralization point. A second image isprojected in a second maximum area rectangle at a second aspect ratio ofthe second image. The second image is projected into the projection areacentered at the centralization point.

As shown in FIG. 2, control module 145 includes, at least,computer-executable process steps for plural modules of this embodiment,including corner detection (CD) module 135, centralization (C) module137, maximum area (MA) module 138, homography transformation (HT) module139 and image display (ID) module 140.

Corner detection (CD) module 135 is constructed to detect a corner ofeach individual projection area projected by each of projectors 50 to 52in order to determine the projection area on the projection surface. Forexample, in the example shown in FIG. 1, CD module is constructed todetect the corners of individual projection areas A, B and Ccorresponding, respectively, to projectors 50, 51 and 52 of theprojector array. The corners of the individual projection areas aredetected by causing digital camera 55 to capture an image of eachindividual projection area projected by each of the projectors in theprojector array, and analyzing the captured image. A virtual Cartesiancoordinate system can be used to designate the coordinates of thecorners and the boundaries of the projection area connecting thecorners. The boundary of the projection area will then be used as alimit on the maximum size of the displayed images within the projectionarea.

Maximum area (MA) module 138 is constructed to identify the aspect ratioof each input image that is to be displayed by the projector array andis also constructed to calculate the coordinates of a maximum arearectangle available within the projection area detected by the CD module135. The maximum area rectangle is determined in which a respectiveinput image can be displayed at its largest size within the projectionarea at the aspect ratio detected and centered at a centralization pointdesignated by the centralization module 137, described below. For thesecond and subsequent input images in a sequence of images, the maximumarea rectangle is further modified by scaling it up or down to centerthe respective maximum area rectangle about the centralization pointdesignated by the centralization module 137. The maximum area rectangleis scaled up or down based on the aspect ratio of the image so that thearea of the rectangle is maximized to fit within the projection areadetected by the CD module while being centered at the centralizationpoint designated by the centralization module 137.

Centralization (C) module 137 is constructed to designate acentralization point around which the first maximum area rectangle,corresponding to the first input image, and all subsequent maximum arearectangles, corresponding to subsequent input images, are centeredduring display of those respective images. C module 137 provides thecentralization point to the MA module to determine the maximum arearectangle.

Homography transformation (HT) module 139 is constructed to derivehomography transformations for projectors 50 to 52 in order tofacilitate keystone correction. HT module 139 derives a homographytransformation, and an inverse of the derived homography transformation,for each of the projectors involved in the projection of each projectedimage. The inverse homography transformation is output to the HT modulefor keystone correction of the input image.

Image display (ID) module 140 is constructed to calculate a modifiedimage based upon the output from the HT module, the MA module, and theinput image itself. Such a modified image is to be the largest image tofit within the projection area at the aspect ratio of the input imageand be centered at the designated centralization point. ID module 140provides the modified image data to each of the projectors 50 to 52 fordisplay on the projection surface.

The computer-executable process steps for control module 145 may beconfigured as a part of operating system 130, as part of an outputdevice driver such as a projector driver, or as a stand-aloneapplication program such as a multiprojector management system. They mayalso be configured as a plug-in or dynamic link library (DLL) to theoperating system, device driver or application program. For example,control module 145 according to example embodiments may be incorporatedin an output device driver for execution in a computing device, such asa projector driver, embedded in the firmware of an output device, suchas a projector, or provided in a stand-alone application for use on ageneral purpose computer. In one example embodiment, control module 145is incorporated directly into the operating system for general purposehost computer 40. It can be appreciated that the present disclosure isnot limited to these embodiments and that the disclosed control modulemay be used in other environments in which control of a multiprojectorsystem is desired.

FIG. 3 is a view for explaining software architecture of control module145 for a multiprojector system according to an example embodiment. Asshown in FIG. 3, CD module 135 controls the multiprojector system suchthat an image is captured of a projection area projected by allprojectors 50 to 52, and analyzes that captured image in order todetermine the extent of the projection area on the projection surface.In particular, CD module outputs coordinates for each of the corners ofeach of the individual projection areas displayed by projectors 50 to52, and corners caused by overlapping individual projection areas.

In this embodiment, the corners of each of the individual projectionareas, such as areas A, B and C in FIG. 1, on the projection surface aredetected by analyzing the captured image using, for example, a Cannyalgorithm to determine the coordinates of each of the corners of theindividual projection areas. Of course, any other suitable method ofdetermining the extent of the projection area on a projection surfacemay be used.

MA module 138 accepts, as input, the coordinates of the corners of eachindividual projection area, the input image data, and the centralizationpoint (if already determined). The input image data includes the aspectratio of the input image. The MA module 138 uses the input image data todetermine the aspect ratio of each input image. The MA module alsoreceives an input from centralization module 137. The input from thecentralization module includes data of a centralization point. Based onthe input image data, the output of the CD module 135, and output fromthe C module 137, the MA module 138 determines and outputs to the HTmodule 139 and the ID module 140, coordinates of a maximum arearectangle. The maximum area rectangle is a rectangle defined bycoordinates in which an image can be displayed within the projectionarea at its maximum size at the aspect ratio of the input image, whilebeing centered about the centralization point. More specifically, MAmodule 138 comprises computer-executable process steps to calculate thecoordinates of a maximum area rectangle for each image on the projectionsurface, taking into account the individual aspect ratios of each inputimage, such that the image is displayed in a maximum area within theprojection area in accordance with the aspect ratio of the input image300, while being centered about the centralization point.

In particular, in this embodiment, the maximum area is calculated byusing a rectangle having the same aspect ratio as input image. Based inpart on the coordinates of the corners and coordinates of the projectionarea, the edges of each maximum area rectangle are determined. Forexample, a system of linear equations can be used to solve for thecoordinates of the corners of the rectangle resulting in dimensions oflength and width that maximize the area of the rectangle. In such acase, the length and width will be related by the aspect ratio. Otherconstraints on the system of equations are the locations of the cornersof the projection area, which can be mapped to a Cartesian coordinatesystem. Alternatively, the length and width of the maximum arearectangle that minimizes the difference of the total area of theprojection area and the area of the rectangle can also be determined.When a centralization point has already been determined by the C moduleand is input to the MA module, an additional constraint is added whichrequires that the center of the maximum area rectangle be at thecentralization point. The addition of the centralization pointconstraint simplifies the system of equations. While the above-discussedprocess has been provided here as an example, any suitable method ofdetermining the maximum area for display may be used.

HT module 139 accepts, as input, the coordinates of the corners of themaximum area rectangle determined by the MA module along with the inputimage data and aspect ratio. Based on these inputs, HT module 139outputs a modified image for display by projectors 50 to 52.

More specifically, HT module 139 comprises computer-executable processsteps to derive homography transformations for each of the input imagesprovided to projectors 50 to 52 in order to facilitate keystonecorrection. HT module 139 derives a homography transformation, and aninverse of the derived homography transformation, for each of theprojectors involved in the projection of the image.

ID module 140 accepts, as input, the coordinates indicating the maximumarea on which an image can be displayed within an object from MA module138, and modified images from HT module 139. Based on these inputs, IDmodule 140 outputs pre-distorted images to each of projectors 50 to 52in the projector array, such that each projector displays theappropriate portion of the image on the maximum area on the projectionsurface, and such that the image is substantially the largest imagepossible given the extent of the projection area, the centralizationpoint, and the aspect ratio of the input image.

More specifically, ID module 140 comprises computer-executable processsteps to cause projectors 50 to 52 to form keystone corrected image 60corresponding to the input image. ID module 140 provides image datawhich has been adjusted by HT module 139 to each of the projectors 50 to52 for display based on the maximum area calculated by MA module 138 foreach image. In particular, ID module 140 scales and shifts each modifiedimage to adjust those images for display in the maximum area.

FIG. 4 is a flow diagram for explaining control of a multiprojectorsystem according to an example embodiment. The process steps shown inFIG. 4 are computer-executable process steps stored on acomputer-readable memory medium such as at 145 on fixed disk 45, and areexecuted by CPU 113 of host computer 40, so as to implement a controlmodule for control of a multiprojector system including multipleprojectors arranged in a projector array. Briefly, according to theprocess steps shown in FIG. 4, a projection area is detected by cornerdetection using an image capture device which captures an image of theprojection surface. The first image is keystone corrected and isprojected in a first maximum area rectangle having a first aspect ratioof the first image. A centralization point is designated as the centerof the maximum area rectangle of the first image. A second, orsubsequent, image is keystone corrected and is projected in a secondmaximum area rectangle having a second aspect ratio of the second image,wherein the second image is projected into the projection area centeredat the centralization point.

In more detail, in step S401, CD module 135 captures an image of theprojection area displayed by all of the projectors in the projectorarray, and analyzes the captured image using a Canny algorithm in orderto detect the extent of the projection area.

In step 402, the aspect ratio of an input image is determined based uponthe input image data. Then, in if it is detected that the input image isthe first image in a sequence of images (“YES” at S403), a maximum arearectangle is determined in step S404 based on the aspect ratio of theimage and the projection area. On the other hand, if it is detected thatthe input image is not the first image in a sequence of images (“NO” atS403), a maximum area rectangle is determined in step S405 based on theaspect ratio of the image, the projection area, and a centralizationpoint determined from the centralization module. In step S406, ahomography matrix is derived for the image to be displayed by each ofthe projectors involved in the projection of the image. In step S407, aninverse homography matrix is derived from the homography matrix derivedin step S406 and are output to the image display module. In step S408the coordinates of the keystone corrected modified image are calculatedby the homography transform module 139.

In step S409 it is determined whether or not the modified imagecorresponds to the first image in a sequence of images. If the modifiedimage is corresponds to the first input image (“YES”, at S409), then instep S410 the centralization point is determined by the centralizationmodule 137 from the maximum area rectangle determined in step S404. Thecentralization point determined in step S410 is used as the location ofthe center of subsequent projected images as well as the center of theprojected first image.

On the other hand, if the modified image does not correspond to thefirst input image (“NO”, at S409), then the maximum area rectangle iscentered about the centralization point and the maximum area rectangleis determined by the maximum area module 138 based on the aspect ratioof the input image, the centralization point determined from the firstimage in step S410, and the projection area.

In step S411 ID module 140 scales and shifts the keystone correctedimages for display based on the maximum area rectangle and thecentralization point. Each modified image is displayed by each ofprojectors 50 to 52 to form image 60 in step S411.

FIGS. 5A and 5B show, schematically as a progression, views of twoimages showing how the maximum area rectangle is determined inaccordance with the control steps shown in FIG. 4 and described above.In particular, FIG. 5A shows the display of the first modified image inthe first image maximum area rectangle 501 in accordance with step S411.The first image maximum area rectangle 501 is positioned in a projectionarea formed by two overlapping individual projection areas, D and E. Thefirst maximum area rectangle 501 is centered at a centralization point,shown as a solid circle, and determined in step S410.

After the first maximum area rectangle 501 is determined, it isdetermined that a second input image exists to be displayed, inaccordance with step S412. The aspect ratio of the second input image isdetermined in accordance with step S402 and a second maximum arearectangle 502 is determined in accordance with step S405. The secondmaximum area rectangle 502 is determined to be centered at thecentralization point and is scaled up around the centralization pointmaintaining the aspect ratio of the second input image. The secondmaximum area rectangle 502 is scaled up to its largest size whileremaining completely within the projection area.

As a result of the scaling of the second maximum area rectangle 502shown in FIG. 5B, a second keystone corrected image can be displayed inthe projection area at its largest size while being centered at thecentralization point, which is common to the first modified image.Displaying the second keystone corrected image at its aspect ratio andcentralizing the second image at a single centralization point areintended to reduce the perception by the viewer that the sequence ofimages jump around different parts of the projection surface and thatthe images are distorted in size.

By way of contrast, FIG. 5C illustrates an example in which the secondmaximum area rectangle is determined without centering the secondmaximum area around the centralization point shown in FIGS. 5A and 5B.In this example, the center of the second maximum area rectangle, andsubsequent maximum area rectangles are not required to be coincidentwith the first maximum area rectangle. Therefore, as shown in FIG. 5C, asecond maximum area rectangle 502 a is determined in similar manner asthe first maximum area rectangle 501. However, the center of theresulting second maximum area rectangle 502 a is not coincident with thecentralization point shown in FIGS. 5A and 5B. When the second keystonecorrected image is projected in this second maximum area rectangle 502a, the center point of that second keystone corrected image will appearto have shifted or jumped when compared to the immediately precedingimage, i.e., the first keystone corrected image. This shift in thecenter points is shown in FIG. 5C by the horizontal arrow showing thedistance between the centralization point shown in FIGS. 5A and 5B andthe center of the second maximum area rectangle 502 a. Such anappearance of projected images jumping is distracting to viewers.

Accordingly, according to the example embodiments described herein, tomitigate the appearance of projected image jumping, the second maximumarea rectangle 502 is determined by maintaining its center at thecentralization point determined based on the first maximum arearectangle 501, as discussed above in connection with FIGS. 5A and 5B.

This disclosure has provided a detailed description with respect toparticular representative embodiments. It is understood that the scopeof the appended claims is not limited to the above-described embodimentsand that various changes and modifications may be made without departingfrom the scope of the claims.

1. A method of displaying images with a projector array, wherein theprojector array comprises a plurality of projectors, which together,project the images into a projection area on a projection surface, themethod comprising: designating a centralization point in the projectionarea; projecting a first image in a first maximum area rectangle at afirst aspect ratio of the first image, wherein the first image isprojected into the projection area centered at the centralization point;and projecting a second image in a second maximum area rectangle at asecond aspect ratio of the second image, wherein the second image isprojected into the projection area centered at the centralization point.2. The method according to claim 1, further comprising: detecting theprojection area by corner detection using an image capture device whichcaptures an image of the projection surface.
 3. The method according toclaim 1, further comprising: determining the first maximum arearectangle at the first aspect ratio within the projection area;identifying the center of the first maximum area rectangle as thecentralization point; and determining the second maximum area rectangleat the second aspect ratio within the projection area, wherein thesecond maximum area rectangle is determined by calculations using thesecond aspect ratio and the centralization point, so as to result in asubstantially maximum area within the projection area centered at thecentralization point.
 4. The method according to claim 3, furthercomprising: determining a first homography matrix based on thedetermination of the first maximum area rectangle; applying a firstinverse homography matrix transform to the first homography matrix;obtaining a first homography-transformed image of the first image basedon the first inverse homography matrix and the first aspect ratio;determining a second homography matrix based on the determination of thesecond maximum area rectangle; applying a second inverse homographymatrix transform to the second homography matrix; and obtaining a secondhomography-transformed image of the second image based on the secondinverse homography matrix and the second aspect ratio.
 5. A controlmodule for a projector system, wherein the multiprojector systemcomprises multiple projectors arranged in a projector array, the modulecomprising: a centralization module constructed to designate acentralization point in a projection area; an image display moduleconstructed to display a first image in a first maximum area rectangleat a first aspect ratio of the first image, wherein the first image isprojected into the projection area centered at the centralization point,and constructed to display a second image in a second maximum arearectangle at a second aspect ratio of the second image, wherein thesecond image is projected into the projection area centered at thecentralization point.
 6. The control module of claim 5, furthercomprising a maximum area module constructed to, determine the firstmaximum area rectangle at the first aspect ratio within the projectionarea, and determine the second maximum area rectangle at the secondaspect ratio within the projection area, wherein the second maximum arearectangle is determined based upon the second aspect ratio and thecentralization point, so as to result in a substantially maximum areawithin the projection area centered at the centralization point.
 7. Thecontrol module of claim 5, further comprising: a corner detection moduleconstructed to detect the projection area by corner detection using animage capture device which captures an image of a projection surface;and a homography transformation module constructed to determine a firsthomography matrix based on the determination of the first maximum arearectangle by the maximum area module, to apply a first inversehomography matrix transform to the first homography matrix, to obtain afirst homography-transformed image of the first image based on the firstinverse homography matrix and the first aspect ratio, and to determine asecond homography matrix based on the determination of the secondmaximum area rectangle by the maximum area module, to apply a secondinverse homography matrix transform to the second homography matrix, andto obtain a second homography-transformed image of the second imagebased on the second inverse homography matrix and the second aspectratio.
 8. The control module according to claim 6, wherein the thecentralization module determines the centralization point based on adetermination by the maximum area module of the first maximum arearectangle, wherein the centralization point is coincident with thecenter of the first maximum area rectangle.
 9. A projector array displayapparatus comprising: a processor with an interface to a projectorarray, wherein the projector array comprises a plurality of projectors,which together, project the images into a projection area on aprojection surface; and a memory storing a program executable by saidprocessor, wherein the program causes the processor to implement amethod of displaying images with the projector array, wherein the methodincludes the steps of: designating a centralization point in theprojection area; projecting a first image in a first maximum arearectangle at a first aspect ratio of the first image, wherein the firstimage is projected into the projection area centered at thecentralization point; and projecting a second image in a second maximumarea rectangle at a second aspect ratio of the second image, wherein thesecond image is projected into the projection area centered at thecentralization point.
 10. The apparatus according to claim 9, whereinthe program stored in the memory further causes the processor toimplement a method further including the step of: detecting theprojection area by corner detection using an image capture device whichcaptures an image of the projection surface.
 11. The apparatus accordingto claim 9, wherein the program stored in the memory further causes theprocessor to implement a method further including the steps of:determining the first maximum area rectangle at the first aspect ratiowithin the projection area; identifying the center of the first maximumarea rectangle as the centralization point; and determining the secondmaximum area rectangle at the second aspect ratio within the projectionarea, wherein the second maximum area rectangle is determined bycalculations using the second aspect ratio and the centralization point,so as to result in a substantially maximum area within the projectionarea centered at the centralization point.
 12. The apparatus accordingto claim 11, wherein the program stored in the memory further causes theprocessor to implement a method further including the steps of:determining a first homography matrix based on the determination of thefirst maximum area rectangle; applying a first inverse homography matrixtransform to the first homography matrix; obtaining a firsthomography-.transformed image of the first image based on the firstinverse homography matrix and the first aspect ratio; determining asecond homography matrix based on the determination of the secondmaximum area rectangle; applying a second inverse homography matrixtransform to the second homography matrix; and obtaining a secondhomography-transformed image of the second image based on the secondinverse homography matrix and the second aspect ratio.
 13. A computerreadable storage medium having stored thereon a plurality ofcomputer-executable instructions, the plurality of instructions whenexecuted by a processor, cause the processor to perform a method ofdisplaying images with a projector array, wherein the projector arraycomprises a plurality of projectors, which together, project the imagesinto a projection area on a projection surface, the method comprisingsteps of: designating a centralization point in the projection area;projecting a first image in a first maximum area rectangle at a firstaspect ratio of the first image, wherein the first image is projectedinto the projection area centered at the centralization point; andprojecting a second image in a second maximum area rectangle at a secondaspect ratio of the second image, wherein the second image is projectedinto the projection area centered at the centralization point.
 14. Thecomputer readable storage medium according to claim 13, wherein themethod further comprises the step of: detecting the projection area bycorner detection using an image capture device which captures an imageof the projection surface.
 15. The computer readable storage mediumaccording to claim 13, wherein the method further comprises the stepsof: determining the first maximum area rectangle at the first aspectratio within the projection area; identifying the center of the firstmaximum area rectangle as the centralization point; and determining thesecond maximum area rectangle at the second aspect ratio within theprojection area, wherein the second maximum area rectangle is determinedby calculations using the second aspect ratio and the centralizationpoint, so as to result in a substantially maximum area within theprojection area centered at the centralization point.
 16. The computerreadable storage medium according to claim 15, wherein the methodfurther comprises the steps of: determining a first homography matrixbased on the determination of the first maximum area rectangle; applyinga first inverse homography matrix transform to the first homographymatrix; obtaining a first homography-transformed image of the firstimage based on the first inverse homography matrix and the first aspectratio; determining a second homography matrix based on the determinationof the second maximum area rectangle; applying a second inversehomography matrix transform to the second homography matrix; andobtaining a second homography-transformed image of the second imagebased on the second inverse homography matrix and the second aspectratio.